Do Mountains Cause Brain Damage?

Scientists have long seen signs of brain damage among certain climbers on Mount Everest and other high peaks, and now a National Institutes of Health researcher worries that even tackling the West’s highest summits could lead to irreversible brain damage.

“It seems that climbers of high mountains, whether weekend warrior or seasoned professional, face returning from the high peaks with a brain that is not in the same condition it was in beforehand,” he writes.

Fields’ column, “Into Thin Air: Mountain Climbing Kills Brain Cells,” is based on a Spanish study published in 2006 in the American Journal of Medicine by Drs. Nicolás Fayed, Pedro J. Modrego and Humberto Morales. Using brain scans, they found evidence of brain damage among climbers on peaks as low as Europe’s Mont Blanc, at 15,870 feet. And that included climbers who showed no outward signs of altitude sickness.

Fields says he worries that also could mean problems for some who scale Fourteeners – American peaks over 14,000 feet. It’s not likely a danger for healthy locals used to living at higher altitudes, he says, but visitors who zip from sea level to the summit within days could face permanent brain damage.

“Your body is remarkable in its ability to react,” Fields says in an interview. “You can react to high altitude quite well, but it takes time. The body’s pretty well adapted to whatever it was evolved to encounter, and it wasn’t evolved to go from sea level to 14,000 feet in one day.” It’s an issue that could even affect some people, like the elderly, on airplane trips where cabins are pressurized to the equivalent of a mountain resort town, he says.

“This study points out the need for more research,” says Fields, a researcher at Porter Neuroscience Research Center in Bethesda, Md., and Editor in Chief of the journal Neuron Glia Biology. “We don’t have data.”

Climbing medicine expert Dr. Peter Hackett, of Telluride, Colo., plans to do that research. He is hoping to launch an expedition in June to North America’s highest peak, Denali, in Alaska, at 20,320 feet, to try to disprove the Spanish study.

“It’s clear to me that you’re taking a great risk in terms of your brain if you climb Everest without oxygen,” says Hackett, director of the Institute for Altitude Medicine and clinical director of the Altitude Research Center at the University of Colorado Medical School. “But to suggest a Fourteener, or Denali, could cause permanent brain damage, which is what these guys suggest, my bias is to say that doesn’t happen.”

The notion of a link between high-altitude climbing and brain damage isn’t new to mountaineers. “There’s a standing joke that those who do it a lot are probably light a few brain cells,” says Steve Bonowski, director of the high-altitude mountaineering section of the Colorado Mountain Club. When he leads trips, including one to China’s Muztagh Ata this summer, he takes his groups up high, then back down again, to get them used to the altitude, he says.

“The old kind of rule of thumb is to climb high and sleep low,” he says.

The Spanish study has raised eyebrows in the mountaineering community, though, by suggesting brain damage could happen on lower peaks and among climbers who seem to be well acclimated. The damage appeared worse among amateurs, but professionals showed damage that researchers believe had accumulated throughout their mountaineering careers.

Using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), they studied the effects on 35 climbers: 12 professionals and 23 amateurs on Everest, Aconcagua in Argentina, Kilimanjaro in Tanzania and Mont Blanc, between France and Italy.

Researchers found 12 of the 13 climbers on Everest had abnormal MRIs. The one amateur in the group showed brain lesions. Climbers on lower peaks also showed signs of brain damage. On Mont Blanc, the lowest, even though none of the seven climbers showed outward signs of mountain sickness, four had abnormal MRIs, one developed lesions and two showed dilations of spaces in the brain, a condition researchers say was most commonly associated with the elderly.

The results led them to conclude that “high-altitude climbing carries a non-negligible risk” of brain damage.

Hackett is skeptical. “My bias is, it’s good for you to be in the mountains,” he says. “It’s good for you to climb Fourteeners. It’s good for you in many ways.”

He called the study’s MRI results inconclusive and says few of the participants were tested beforehand, so researchers had nothing to compare them to. Hackett says the meaning of the wider brain spaces isn’t clear to scientists, and since the climbers weren’t given cognitive tests, it’s unclear if their behavior was at all affected.

“I climbed Everest,” Hackett says. “I blame all sorts of stuff on climbing Everest. But how do you really know unless you apply the scientific method?”

With two Everest attempts and several Himalayan climbs under his belt, Aspen, Colo., mountaineer Steve Marolt says he’s noticed mental effects for two to three months after high-peak climbs. “There’s no question. There’s definitely memory loss,” he says. “You can’t remember telephone numbers. You have to concentrate a little more to remember names.”

Those symptoms go away, though, he says. Amid the many dangers facing mountaineers, Marolt says, the threat of brain damage is “not enough to dissuade me from going again, let’s put it that way. Sure, you think about it. But I’m sure a lot of my friends out smoking dope and partying have burned a lot more brain cells than I have climbing.”

The danger is not discouraging Fields, the NIH researcher, either. He’s planning to climb Washington’s Mount Rainier, at 14,410 feet, this summer, but he’s planning to take it slowly.

“The thing is, climbing is dangerous,” he says. “Your fingers can turn black and fall off, yet people still do it. … Climbing is not about taking risks. It’s about knowing the risks and overcoming them.”

The problem in this case, he says, is that scientists don’t know what the risks are, so climbers don’t know what precautions to take.

“Everyone who climbs knows that high altitude is a problem,” says Fields. “Even backpackers know it. But what do we do? We just go by the seat of our pants and see what works.”

“What you don’t know can’t hurt you”, might make a catchy tune for whistling in the dark. The fact is, none of the climbers in the study believed they had suffered brain injury, but 12 out of 13 returning from Everest came back with physical damage to their brain. The damage was permanent, and climbers attempting lower peaks also suffered the same brain injury. From a scientific viewpoint, the brain damage is not a mystery (20-20 hind-sight). The problem is that no one gets an MRI brain scan if they don’t feel ill. So no wonder we didn’t know.

Many things once believed to be safe are later found to be dangerous. The drug Viox is a recent example, but there is a very long list extending through sugar substitutes to thalidomide. At one time smoking cigarettes was not only believed to be safe; it was touted as having health benefits.

There is some interesting discussion related to the subject of high altitude and brain damage on the Scientific American website, particularly related to airline travel.